Converting hydrocarbon oils



Oct. 8, 1935. R. F. mo 2,016,949

CONVERTING HYDROCARBON OILS Filed May 19, 1951 I E/CH/IQD. F 720"INVENTOR HA9 ATTOR N EY Pmmd'oa. s, 1935 UNITED ST T S PATENT OFFICEcoma'rmc nrn'aoc'aanon oms .Richard F. Trow, Port Arthur, Tex., asslgnorto The Texas Company, New York, N. Y., a corporation of DelawareApplication May 19, 1931, Serial No. 538,592

Claims;

I .as an unclean gas oil, is contacted with hot from the distillationzone is combined with the heated products from the heater and themixture is subjected to an appropriate time of digest in enlarged zones.The resultant hot vapors are delivered to the distillation zone toeffect distillation of the charge oil and a residue, being deposited inthe digestion zones, is subjected to autogenous distillation to producean ultimate residue and a vaporous portion which is preferably condensedand delivered to the cracked vapor dephlegmating means.

The various advantages and objects'of my invention will be apparent fromthefollowing description taken in c'onnectionwith the accompanyingdrawing which illustratesdiagrammatically a preferred embodiment ofapparatus suitablefor practicing the process.

Element l is a heater, 2 and 3 are reaction vessels, 4 is a combinationreaction vessel, distillation tower-and scrubber. 5 is a flashdistillationvessel, 6 is a dephlegmator, 1 is a reflux condenser, 8 is afinal condenser and 9 is an accumulator vessel. 7 p

A pipe l5 conveysfresh charge oil thru a coil I6 and optionally thru acoil l'l into the vessel 4. A vapor line 20 connects the top of thevessel 4 with the lower portion of the dephlegmator 6. J

A vapor line 2| and a run back line 22 connect the upper portion of thedephlegmator with the lower portion of the reflux condenser l. A finalvapor line 23 leads to the final condenser 8 and a line 24 leads fromthe condenser to the accumulator 9 which has a liquid outlet 25 and agas outlet 26.

A pump 3| takes suction-thru a line 30, fromthe bottom of thedephlegmator and discharges thru a line 32into the heater I. ,A transferline 33 connects the heater with the upper portion of the vessel 2 andlines 34 and 35 connect the vessels 2 and 3, and 3 and 4 respectively.

Drawoif lines 40 and 4l from vessels 2 and 3,

respectively, lead into a manifold line 43 which is connected to thelower portion of the vessel 5 5. A draw-off line 44 leads from thebottom of the vessel 4 to a pump 45 which discharges thru a line 46 intothe transfer line 33. A discharge line 41 from the vessel 5 leads tostorage or other means not shown. Jump over lines 48 and 49 are providedleading into the discharge line 41. In order to furnish cooling to theseveral vessels in which scrubbing and fractionation is carried onreturn lines are provided .to return a cooling liquid. In some caseswhere the desirable reflux' medium may be so 'warm as to requireconsiderable quantities of it cooling coils are provided to reduce theamount of cooling medium to be, pumped back.

A- branch line 65 is provided from the line 32 by which a portion of theclean gas oil may be pumped back thru a cooler 66 into the upper portionof the vessel 4. Another'branch line 10 is provided from the line 32'thru a cooler H to the baiiles in the dephlegmator 6.

A connection from the condensate discharge from the pump 6| is providedto the upper portion of the vessel 5.

Another connecting line 15 together with a pump 16 is provided forpumping a trapped out 30. portion ofthe final condensate back to thereflux condenser I.

When beginning to operate, a suflicient amount of clean oil maybe drawnthru a line 29 from a 'source not shown and pumped into the heater I.

After operating conditions are established, a switch may be made to thefresh charge oil which is drawn in thru the line I5. I 4 I In apreferred mode of operation ages oil of say 25 B. gravity may be chargedto a baille plate in the upper portion of the vessel 4 where it iscontacted with rising hot cracked vapor from' the crackingzone. A virgingas oil fraction of this gravity obtained from the distillation of crudepetroleum will" usually containsome heavy constituents which will causethe distillation tem-\ perature to rise sharply when distilling it atatgj mospheric pressure. The heavier constituents of the gas oil beingthe most refractory constitute the portion of a 5 fresh charge whichdecomposes most readily to form pitch or coke and gas and while it wouldnot be practicable to subject this portion to the high temperaturesatwhich the high anti-knock motor fuel is produced it is possible tosubject it to milder conditions and decompose it into a somewhat lighterproduct the major portion of' 'which would be a lighter more refractorygas oil which could be subjected to the high temperature.

Thus as the charge oil delivered into the vessel 0 wardly incountercurrent to the hot cracked vapor the lighter portion, which maycomprise 90 to 95 percent of the charge oil, is vaporized. The

vessel together with any residue which may be precipitated from the hotcracked vapor.

The total vaporin the vessel 4 is subjected to a scrubbing step inthe'top of the vessel, without substantial cooling, to remove such tarry'and heavy liquid particles as might have become entrained therewith.Such substance as this it is known will decompose rapidly into ookeyparticles which adhere readily to the heater tubes with deleteriousefiect. Thus it is desirable that the I vapor withdrawn overhead fromthe vessel 4 contain only a ratherv highly refractory clean gas oilfraction which has a relatively flat distillation curve toward the end.

The vapor is delivered into the dephlegmator in which it undergoesconventional fractionation toproduce an overhead vaporousmotor fuel anda clean gas oil condensate.

The condensate is removed continuously almost as soon as it is depositedand charged to the heater, only enough being-held in the dephlegma torto insure a liquid seal andsmooth regular operating conditions. Thetemperature is raised in the heater to approximately 980 F. at which theclean oil is substantially all vapor at the pressure employed which ispreferably about 400 pounds per square inch at the outlet.

It is to be understood that the residual portion of the virgin chargedeposited in the vessel 4 does contain some slight amount ofconstituents which may be further decomposed under more favorableconditions. As this residual portion is somewhat cooler than the highlyheated gas oil it is of advantage to commingle the two for while it isnecessary to heat the residual portion to effect its furtherdecomposition it is also desirable to quench the highly heated oil toprevent its further decomposition into coke and gas. By combining thetwo an average temperature of say 900 F. 'in the transfer line 3 isattained.

The combined oil and vapor is delivered into the upper portion of thefirst reaction vessel 2 where additional quantities of liquid arevaporized and some of the remaining liquid portion is also atomized, andpassedinto the vessel I. The vapor finally emerging from the top of thevessel 3 is delivered under considerably reduced pressure, e. g. 150pounds per square inch, into the vessel 4. Thus after a desirable timeof digest in the vessels 2 and 3 where an appropriate temperature ismaintained to effect conversion of the combined vapor and mist particlesthe reaction is stopped by reducing'the pressure and temperaturesimultaneously upon discharging into the vessel4. The cracked vapor,atthe reduced temperature, furnishes a heating medium for the freshcharge being delivered into the vessel 4 which is hot enough to vaporizethe lighter and crack and vaporize the heavier portion as previously de-4 spreads out over the battles and is moved down- The residue which isdeposited in the vessel 2 and 3 is almost immediately withdrawn and isdelivered into an autogenous distillation zone of considerably reducedpressure, e. g. 10 pounds per square inch more'or less, where theremaining 5 gas oil fraction is flashed of! and the final residue isdischarged from the system. The residue as it is precipitated in thereaction vessels 2 and 3 will contain some small amount of gasolinefraction as well as gas oil altho the preponderance of the materialdistillate in the autogenous distillation step will be the latter. Thevapor developed in this step is scrubbed in the upper portion of thisvessel to remove all traces of tarry and cokey substance. 'The cleanvapor is then passed thru a condenser 60 from which a pump 6| takessuction and discharges the entire condensate to the uppermost of aseries of bailies into the dephlegmator 6. Here'the condensateisfractionated, along with the vapors entering thru the pipe 20,- toproduce motor fuel as vaporleaving the top of the tower 6 and acrackingstock as condensate collecting at the bottom of the tower.

I The total combined vapor from thedephlegma tor 8 is subjected toadditional condensation in the reflux condenser I and a final overheadvapor is condensed in the condenser 8. As there will be asmall amount ofnon-condensible gas developed in the cracking it is preferable to passthe products from the condenser 8 into an accumu- 3 lator in which thegas and' liquid are'separated and each is discharged to further meansthru their respective outlet lines.

While Ihave described a preferred mode of operation it is to beunderstood that no limitation 3 'is'thus intended to the scope of myinvention which is to. belimited only by the appended claims. L I

WhatIclaim is:

1. The process oficonverting higher boiling 40 hydrocarbon oils intolower boiling ones that comprises introducing 'charging stock. to acolumnar distillation zone maintained a under supcratmospheric pressureand fed with vapors at high cracking temperature from an enlargedcracking zone to thereby dephlegmate the vapors and to subjectthecharging stock to-vaporization to vaporize portions thereof' adaptedfor cracking at high temperatures and to subject unvaporized portions ofthe charging stock to 59 -cracking temperatures to effect cracking withthe formation of an ultimate residual 011 maintained at crackingtemperature and an overhead vapor fractioncomprising vaporizedcomponents of the charging stock as well 'as cracked constituents,subjecting the overhead vapor fraction to fractionation to form a finallight distillate and a gas oil condensate, passing said gas oilcondensate through a heating coil wherein the condensate oil issubjected to a high crack- 50 ing temperature to effect a high rate ofcracking. combining residual oil withdrawn from. the columnardistillationzone with the highly heated products from said heating coiland directing the combined products into an enlarged cracking zonewherein separation of vapors from liquid occurs and wherein crackingtemperature under a superatmospheric pressure materially higher thanthat of said columnar distillation zone is maintained and from which theseparated vapors 7 residual oil to said heatin coil.

vaporized portions of the charging stock to cracking temperatures toeffect cracking with the formation of an ultimate residual oilmaintained at cracking temperature and an overhead vapor fractioncomprising vaporized components of the charging stock as well as crackedconstituents, subjecting the overhead vapor fraction to fractionation toform a final light distillate and a gas oil condensate, passing said gasoil condensate through a heating coil wherein the condensate oil issubjected to a high cracking temperature to effect a high rate ofcracking, combining residual oil withdrawn from the columnardistillation zone with the highly heated products from said heating coiland directing the combined products into an enlarged cracking zonewherein separation of vapors from liquid occurs and wherein crackingtemperature under a superatmospheric pressure of upwards of 400 poundsand materially higher than that of said columnar distillation zone ismaintained and from which the separated vapors are expanded into saidcolumnar distillationezone, and withdrawing liquid from said enlargedzone at a rate adequate to prevent accumulation of liquid thereinwithout conducting any of the residual oil to said heating coil.

3. The process of converting higher boiling hydrocarbon oils into lowerboiling ones that comprises introducing charging stock to a columnardistillation zone maintained under superatmospheric pressure and fedwith vapors at high cracking temperature from an enlarged cracking zoneto thereby dephlegmate the vapors and to subject the charging stock atfirst to vaporization to vaporize portions thereof adapted for crackingat high temperatures and finally to subject unvaporized portions of thecharging stock to increased temperatures to effect cracking with theformation of an ultimate residual oil maintained at cracking temperatureand an overhead vapor fraction comprising vaporized components of thecharging stock as well as cracked constituents, subjecting the overheadvapor fraction to fractionation without any material reduction inpressure to form a; final light distillate and a gas oil condensateadapted to be completely vaporized without the formation of coke,passing said gas oil condensate in a stream through a heating coil tosubject the oil to cracking in the vapor phase, combining residual oilwithdrawn from the columnar distillation zone with the highly heatedproducts from said heating coil and directing the combined products intoan enlarged cracking zone wherein separation of vapors from liquidoccurs and wherein cracking temperature under a superatmosphericpressure materially higher than that of said columnar distillation zoneis maintained and from which the separated vapors are expanded into saidcolumnar distillation zone, withdrawing liquid from said enlarged zoneat a rate adequate to prevent accumulation of liquid therein, withoutconducting any residual oil to said heating coilexpanding the residualoil thus withdrawn into an-auto-distillation zone maintained under amaterially lower pressure than that of said columnar distillation zone,obtaining a condensate from the resultant vapors and subjecting thecondensate to fractionation at increased pressure with the vapors fromthe columnar distillation zone.

4. A hydrocarbon oil cracking process which comprises passing arelatively light and clean distillate, formed as hereinafter set forth,

through a heating zone and heatingthe same therein to crackingtemperature under pressure, discharging the heated distillate into areaction zone maintained under cracking conditions of temperature andpressure, removing vapors from the reaction zone and subjecting the sameto primary dephlegmation in direct contact with fresh charging oil forthe process, introducing the resultant mixture of unvaporized chargingoil and primary reflux condensate, without passage through said heatingzone and without prior heating to cracking temperature, directly intothe reaction zone and commingling the same with the heated distillatetherein, removing unvaporized oil from the reaction zone and flashdistilling the same by pressure reduction, combining the vaporsuncondensed by the primary dephlegmation with overhead products from theflash distillation in a secondary dephlegmation zone out of directcontact with charging oil thereby forming a secondary reflux condensateun-, admixed with heavy oil, supplying the secondary reflux condensate,unadmixed with fresh charging oil, to the heating zone as saidrelatively light and clean distillate, and finally condensing as aproduct of the process the vapors uncondensed by the secondarydephlegmation.

5. A hydrocarbon oil cracking process which comprises passing arelatively light and clean distillate, formed as hereinafter set forth,through a heating zone and heating the same therein to crackingtemperature under pressure, discharging the heated distillate into areaction zone maintained under cracking conditions of temperature andpressure, removing vapors from the reaction zone and subjecting the sameto primary dephlegmation in direct contact with fresh charging oil forthe process, introducing the resultant mixture of unvaporized chargingoil and primary reflux condensate directly into contact with the heateddistillate discharged from said heating zone so that the heateddistillate and mixture of unvaporized charging oil and primary refluxcondensate are in contact at a cracking temperature in said reactionzone. removing unvaporized oil from the reaction 'zone at a rateadequate to prevent the accumulation of liquid therein and flashdistilling the same by pressure reduction, combining the vaporsuncondensed by the primary dephlegmation with overhead products from theflash distillation in a secondary dephlegmation zone out of directcontact with charging oil thereby forming a secondary reflux condensateunadmixed with heavy oil,

supplying the secondary reflux condensate, un-

admixed with fresh charging oil, to the heating zone as said relativelylight and clean distillate and iinallycondensing as a product of theprocess the vapors uncondensed by the secondary dephelgmation.

RICHARD F. TROW.

